1. Field of the Invention
The present invention relates to a new catalyst for the polymerization of olefins which exhibits a high catalytic activity and is capable of producing a highly stereospecific olefin polymer and to a specific solid catalyst component used for the catalyst. More particularly, the present invention relates to a new catalyst for the polymerization of olefins which is useful for producing highly stereoregular olefin polymers in a high yield and maintains its catalytic activity and stereospecific performance for a prolonged period of time and which comprises a specific solid catalyst component, a disubstituted or tetrasubstituted piperidine derivative and an organoaluminum compound, as well as the specific solid catalyst component for the catalyst, which can be prepared from magnesium, an alkyl monohalide, a phthalic diester and titanium tetrachloride according to a series of specific treatments.
2. Description of the Prior Art
In recent years, a number of new type catalysts for the polymerization of olefins including propylene were developed and proposed, wherein a titanium active ingredient supported together with an electron donor on magnesium chloride is used, in place of the conventionally known titanium trichloride catalyst component.
Among these new type catalysts, those developed at the earliest stage were comprised of a product obtained by copulverizing a complex of titanium tetrachloride and an organic monocarboxylic acid ester as an electron donor with magnesium chloride or of a product obtained by treating a copulverized product of magnesium chloride and an organic monocarboxylic acid ester as an electron donor with titanium tetrachloride (Japanese Laid-open Patent Appln. No. Sho. 50-126590).
However, these catalysts cannot be said to possess characteristics satisfactory for the use in an industrial scale. In order to improve various characteristics of the catalysts, a number of improvements have been proposed hitherto, for example, including the use of diethoxymagnesium, the use of a specific compound as an electron donor and modifications made for a method for combining the above ingredients or a contact means between the ingredients. In Japanese Laid-open Patent Appln. No. Sho. 59-12904, for example, there is disclosed a catalyst component for such catalysts which is derived from a magnesium compound of the formula: Mg(OR).sub.2 where R is an alkyl, cycloalkyl or aryl group, an aromatic monocarboxylic ester and a titanium compound of the formula: TiX.sub.4 where X is a halogen atom. In Japanese Laid-open Patent Appln. No. Sho. 54-94590, for example, there is disclosed a modified process wherein a catalyst component is prepared by bringing a magnesium dihalide treated with an electron donor into contact with a tetravalent titanium compound having at least one halogen atom optionally with an electron donor, and the resultant catalyst component is then combined with an organoaluminum compound, an ester of an aromatic monocarboxylic acid and a compound of the formula: M--O--R (wherein M is a metal belonging to the Groups I-A, II-A, II-B, III-A, III-B, IV-A and IV-B of the Periodic Table and R is hydrogen or a hydrocarbyl group) to prepare a catalyst for the polymerization of olefins which is improved to have resistance to deactivation. In Japanese Laid-open Patent Appln. No. Sho. 57-63310, there is disclosed a process for the polymerization of propylene with the aid of an improved catalyst which is derived from a catalyst component comprised of various esters as an electron donor, magnesium chloride in an activated form and a titanium compound; a compound containing a Si--O or Si--N linkage and an organo-aluminum compound. These catalysts are slightly improved in catalytic performance but do not reach a practically satisfactory level in catalytic performance and quality of the resultant polymer.
However, the improved processes recently proposed have also such drawbacks that chlorine contained in the magnesium chloride predominantly used as the carrier in the prior arts as well as a halogen atom contained in the titanium halide give bad influence on the resultant polymer. In these processes is required, therefore, high catalytic activity which is indeed high enough to make the influence of chlorine substantially negligible or reduction in the amount of magnesium chloride contained in the catalyst component.
In the polymerization of olefins in an industrial scale, especially in the production of stereoregular polymers in a commercial scale from propylene, butene-1 or the like olefin, it is usually indispensable to use an electron donor such as an ester of an aromatic monocarboxylic acid for a catalyst containing magnesium chloride as a carrier and in combination with an organoaluminum compound. In this case, it is necessary to use an ester of an organic monocarboxylic acid in an extremely large amount in the polymerization process, thus resulting in such a new problem that the ester imparts its peculiar esteric odor to the resultant polymer. What is more, a serious problem arises in the use of such catalyst. In the so-called supported catalyst having high catalytic activity, such as a catalyst containing magnesium chloride as a support, the activity of the catalyst at the initial stage of polymerization is certainly high but is considerably deactivated with the lapse of time, thus incurring a problem in process operations. Consequently, the use of the catalyst of this type is substantially impossible for the purpose of block copolymerization where a relatively longer polymerization time is required.
To improve this drawback, a modified process is proposed in the above mentioned Japanese Laid-open Patent Appln. No. Sho. 54-94590. As is evident from the disclosure of this reference, it is required in this process to use an ester of an organic monocarboxylic acid not only in the preparation of the catalyst but also on polymerization. In general, the ester of an organic monocarboxylic acid contained in the catalyst is decreased by the treatment with the titanium halide or the washing with an organic solvent to such an amount that the esteric odor of the resultant polymer is almost negligible. It is a current status, however, that the amount of the ester of an organic monocarboxylic acid used in the polymerization step of olefins is much more than that contained in the catalyst so that almost all of the ester will be included in the resultant polymer when the polymerization is carried out in a gaseous or liquid monomer. It can be said, therefore, that the problem of odor in the resultant polymer will not be solved so far as the ester is used in the polymerization step. As is evident from Example 1 (A), (B) and (C) of this reference, the process disclosed therein requires troublesome and complicate operations in the preparation of the catalyst and the polymerization of olefins. Further, the catalyst itself is not satisfactory from the practical point of view as described above, particularly in maintaining the activity.
Under the above circumstances, therefore, there is a great demand in this art for developing a new catalyst for the polymerization of olefins which is markedly improved in any of the polymerization activity, stereospecific performance, maintaining of the activity for a long period of polymerization time and influence of chlorine on the resultant polymer to a satisfactory level in the actual commercial scale production of olefin polymers, especially stereoregular olefin polymers always in a high yield. Till now, however, such demand has not yet been fulfilled.